Panel assembly and method of forming same

ABSTRACT

A panel assembly includes an outer member and an inner member, which overlap each other and jointly have an edge that includes a distal end portion of the outer member and a distal end portion projecting from an end of the inner member. The distal end portions are fastened together by sheet metal seaming. Boundary regions of the inner member between the distal end portion, which is seamed, and the end, which is not seamed, have respective clearances defined in the end, and which are spaced away from a seaming range in which the distal end portions are seamed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2013-142241 filed on Jul. 8, 2013, thecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a panel assembly made up of an outermember and an inner member, which overlap each other and jointly have anedge that includes a distal end portion of the outer member and a distalend portion projecting from an end of the inner member, the distal endportions being fastened together by sheet metal seaming. The presentinvention also relates to a method of forming such a panel assembly.

2. Description of the Related Art

Heretofore, in the automobile industry, panel assemblies, which are madeup of an outer panel (outer member) and an inner panel (inner member)that overlap each other and have respective edges fastened together,have widely been used as engine hoods, trunk lids, doors, etc.

Certain panel assemblies of the type described above may be of athree-dimensional shape having different curvatures on the edgesthereof, or may be made up of panels having portions of differentrigidities, shapes, and other qualities. A panel assembly has beenproposed having edges of excellent appearance, and which is made up ofmembers fastened together with high strength (see Japanese Laid-OpenPatent Publication No. 2008-105083).

The proposed panel assembly has a seamed edge having a first shape and asecond shape. The first shape is a seamed shape in which an end of afirst panel member is included in a second panel member, and an end ofthe second panel member is included in the first panel member. Thesecond shape is a seamed shape in which an end of the second panelmember is included in the first panel member, but an end of the firstpanel member is not included in the second panel member.

SUMMARY OF THE INVENTION

As shown in FIG. 10 of the accompanying drawings, one panel assembly ismade up of an outer panel 1 and an inner panel 2. The outer panel 1 andthe inner panel 2 are fastened together by sheet metal seaming. Theinner panel 2 has a distal end portion 2 b that projects from an end 2 athereof toward a distal end portion 1 a of the outer panel 1.

The inner panel 2 overlaps and is spaced inwardly from the outer panel1. In order to fasten the outer panel 1 and the inner panel 2, thedistal end portion 1 a of the outer panel 1 is curled initially towardthe inner panel 2. As the distal end portion 1 a is curled, the distalend portion 1 a encloses the distal end portion 2 b of the inner panel 2and is continuously curled up to an end line 3.

The distal end portion 2 b of the inner panel 2 has a forming width thatincreases at boundary regions 4 between the distal end portion 2 b andthe end 2 a. Therefore, when a curling punch is used to curl the distalend portions 1 a, 2 b, the curling punch is subjected to excessiveresistance (resistive load per unit width×forming width) at the boundaryregions 4. As a result, the resultant seamed edge is likely to have apoor appearance due to scratches, dents, and other damage caused byimproper biting engagement with the curling punch.

It is an object of the present invention to provide a panel assembly, aswell as a method of forming such a panel assembly, which is capable ofreducing the resistance that a curling punch is subjected to when thecurling punch is used to form the panel assembly, whereby the panelassembly exhibits an improved appearance.

According to the present invention, there is provided a panel assemblycomprising an outer member and an inner member, which overlap each otherand jointly have an edge that includes a distal end portion of the outermember and a distal end portion projecting from an end of the innermember, the distal end portions being fastened together by sheet metalseaming.

Boundary regions between the distal end portion, which is seamed, andthe end, which is not seamed, have respective clearances defined in theend, and which are spaced away from a seaming range in which the distalend portions are seamed.

According to the present invention, there also is provided a method offorming a panel assembly having an outer member and an inner member,which overlap each other and jointly have an edge that includes a distalend portion of the outer member and a distal end portion projecting froman end of the inner member, the distal end portions being fastenedtogether by sheet metal seaming. The method comprises the steps offorming, in boundary regions between the distal end portion, which isseamed, and the end, which is not seamed, respective clearances definedin the end, and which are spaced away from a seaming range in which thedistal end portions are seamed, placing the inner member and the outermember in overlapping relation to each other while the distal endportion of the inner member is spaced inwardly from the distal endportion of the outer member, curling the distal end portion of the outermember and the distal end portion of the inner member, and fastening thedistal end portion of the outer member and the distal end portion of theinner member together by way of sheet metal seaming.

As described above, the boundary regions between the distal end portionand the end of the inner member have the respective clearances, whichare defined in the end and spaced away from the seaming range. When acurling punch curls the distal end portion of the outer panel, therebycausing the distal end portion to include and curl the distal endportion of the inner panel, the resistance that the curling punch issubjected to during the curling action is not increased. Consequently,with a simple structure and process, the load imposed on the curlingpunch when the curling punch curls the inner panel can effectively bereduced. Thus, the edges are prevented from being subjected to improperbiting engagement with the curling punch, and the edges have a neatappearance.

The above and other objects, features, and advantages of the presentinvention will become more apparent from the following description whentaken in conjunction with the accompanying drawings, in which apreferred embodiment of the present invention is shown by way ofillustrative example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, partially cut away, of a panel assemblyaccording to an embodiment of the present invention;

FIG. 2 is an elevational view as seen from the direction indicated bythe arrow A in FIG. 1;

FIG. 3 is a cross-sectional view of the panel assembly taken along lineIII-III of FIG. 1;

FIG. 4 is a perspective view of a principal part of the panel assembly;

FIG. 5 is a plan view of a principal part of the panel assembly;

FIG. 6 is a plan view of an outer panel and an inner panel, whichoverlap each other, of the panel assembly;

FIG. 7 is a fragmentary cross-sectional view showing the outer panel andthe inner panel, which are to be curled;

FIG. 8 is a fragmentary cross-sectional view showing the outer panel andthe inner panel as they are being curled;

FIG. 9 is a fragmentary cross-sectional view showing the outer panel andthe inner panel as they are being seamed; and

FIG. 10 is a fragmentary perspective view showing an outer panel and aninner panel, which are curled and seamed according to the related art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, a panel assembly 10 according to an embodiment ofthe present invention is constructed as a rear door of an automobile,for example. Although not shown, the panel assembly 10 may beconstructed as another automobile component, such as an engine hood, atrunk lid, a front door, or the like.

The panel assembly 10 is made up of an outer panel (outer member) 12 andan inner panel (inner member) 14, which overlap each other. The panelassembly 10 has edges 16, each of which includes seamed edges of theouter panel 12 and the inner panel 14. The edges 16 of the panelassembly 10 extend three-dimensionally within desired ranges of theautomobile rear door.

In the panel assembly 10, the inner panel 14, for example, serves as awindow frame 18 of the automobile rear door. The inner panel 14 is madeof an iron-based material, for example. The outer panel 12 is made of analuminum alloy, for example. Each of the outer panel 12 and the innerpanel 14 is a metal sheet punched out in a desired shape.

The edges 16 extend three-dimensionally within the ranges of theautomobile rear door, which are represented by the cross-hatched stripsF shown in FIG. 2. Alternatively, the edges 16 may extendthree-dimensionally fully around the automobile rear door.

As shown in FIGS. 1 and 3 through 5, the outer panel 12 and the innerpanel 14 are seamed at each of the edges 16, in a state in which theouter panel 12 has a distal end portion 12 a contained within the innerpanel 14, and the inner panel 14 has a distal end portion 14 a containedwithin the distal end portion 12 a of the outer panel 12.

As shown in FIGS. 4 and 5, the distal end portion 14 a of the innerpanel 14 projects from an end 14 b thereof. The distal end portion 14 ais of a rectangular shape having a predetermined forming width H. Amongareas of the inner panel 14, the distal end portion 14 a thereof is anarea to be seamed, whereas the end 14 b thereof is an area that is notseamed.

According to the present embodiment, boundary regions between the distalend portion 14 a and the end 14 b have respective clearances 20 a, 20 b,which are defined in the end 14 b, and are spaced away from a seamingrange (refer to the forming range shown in FIG. 5). The clearances 20 a,20 b are defined as arcuately curved recesses in the end 14 b. Theclearances 20 a, 20 b may be formed integrally in the end 14 b when theinner panel 14 is pressed to shape.

A method of forming the panel assembly 10 will be described below.

As shown in FIG. 6, the outer panel 12 and the inner panel 14 are placedin overlapping relation to each other. At this time, the distal endportion 12 a of the outer panel 12 projects a predetermined lengthoutwardly more than the distal end portion 14 a of the inner panel 14.

Next, as shown in FIG. 7, the outer panel 12 and the inner panel 14,which overlap each other, are placed on a curling block 22. The distalend portion 12 a of the outer panel 12 and the distal end portion 14 aof the inner panel 14 are bent arcuately beforehand, thereby providingflanges. The outer panel 12 and the inner panel 14 are held underpressure on the curling block 22 by a non-illustrated pressing pad.

A curling punch (curling die) 26, which has a curling surface 24 in theform of a curved surface, is slidably placed on the curling block 22.Thereafter, the curling punch 26 is moved in the direction of the arrowin FIG. 7 (forming direction) on the curling block 22, so as to causethe curling surface 24 to start curling the distal end portion 12 a ofthe outer panel 12.

As the curling punch 26 moves further in the direction of the arrow, thedistal end portion 14 a of the inner panel 14 becomes entangled thereinand starts to be curled by the distal end portion 12 a of the outerpanel 12, which is being curled progressively by the curling punch 26.When the distal end portion 14 a is curled through the forming range, asshown in FIG. 8, the distal end portions 12 a, 14 a are seamed into anedge 16, which has a substantially circular cross-sectional shape. Theedge 16, which is formed in the foregoing manner, is made up of amaximum of five vertically stacked panel layers. However, the edge 16may be made up of a maximum of four vertically stacked panel layers.

Thereafter, as shown in FIG. 9, the curling punch 26 is removed, and aseaming punch 30 having a seaming surface 28 is applied to the edge 16on the curling block 22. More specifically, the seaming punch 30 ismoved downwardly in the direction of the arrow in FIG. 9, therebydeforming the edge 16 into a flat shape, and seaming the curled distalend portions 12 a, 14 a together. At this time, the edge 16 has thecross-sectional shape shown in FIG. 3.

According to the present embodiment, as shown in FIGS. 4 through 6, theboundary regions of the inner panel 14 between the distal end portion 14a and the end 14 b have the respective clearances 20 a, 20 b, which aredefined in the end 14 b and are spaced away from the seaming range.Therefore, the forming width H of the distal end portion 14 a, which isseamed, is kept constant, or the forming width H is prevented fromincreasing at the boundary regions.

When the curling punch 26 curls the distal end portion 12 a of the outerpanel 12, thereby causing the distal end portion 12 a to include andcurl the distal end portion 14 a of the inner panel 14, the resistancethat the curling punch 26 is subjected to during the curling action isnot increased. Consequently, with a simple structure and process, theload imposed on the curling punch 26 when the curling punch curls theinner panel 14 can effectively be reduced.

Since the load imposed on the curling punch 26 when the curling punchseams the distal end portions 12 a, 14 a can also be reduced, the seamededges 16 are shaped smoothly without irregularities such as convexitiesand concavities. Thus, the edges 16 are prevented from being subject toimproper biting engagement with the curling punch 26, and the edges 16have a neat appearance.

The panel assembly and the method of forming the panel assemblyaccording to the present invention may also be applied to various otherproducts apart from automobile components.

With the method of forming the panel assembly according to the presentinvention, the distal end portion 12 a of the outer panel 12 and thedistal end portion 14 a of the inner panel 14 are curled to form theedges 16, each of which has a substantially circular cross-sectionalshape. Among the curled edges 16, only portions thereof that lie outsideof the ends of the outer panel 12 may be deformed into a flat shape byseaming.

Although a preferred embodiment of the present invention has beendescribed in detail above, it should be noted that various changes andmodifications may be made to the embodiment without departing from thescope of the invention as set forth in the appended claims.

What is claimed is:
 1. A panel assembly comprising: an outer member andan inner member, which overlap each other and jointly have an edge thatincludes a distal end portion of the outer member and a distal endportion projecting from an end of the inner member, the distal endportions being fastened together by sheet metal seaming, whereinboundary regions of the inner member between the distal end portion,which is seamed, and the end, which is not seamed, have respectiveclearances defined in the end, and which are spaced away from a seamingrange in which the distal end portions are seamed.
 2. The panel assemblyaccording to claim 1, wherein the clearances are defined as arcuatelycurved recesses in the end.
 3. A method of forming a panel assemblyhaving an outer member and an inner member, which overlap each other andjointly have an edge that includes a distal end portion of the outermember and a distal end portion projecting from an end of the innermember, the distal end portions being fastened together by sheet metalseaming, the method comprising the steps of: forming, in boundaryregions of the inner member between the distal end portion, which isseamed, and the end, which is not seamed, respective clearances definedin the end, and which are spaced away from a seaming range in which thedistal end portions are seamed; placing the inner member and the outermember in overlapping relation to each other while the distal endportion of the inner member is spaced inwardly from the distal endportion of the outer member; and curling the distal end portion of theouter member and the distal end portion of the inner member, andfastening the distal end portion of the outer member and the distal endportion of the inner member together to form the edge by way of sheetmetal seaming.
 4. The method according to claim 3, wherein theclearances are defined as arcuately curved recesses in the end.